Over the past three decades, since the inception of the integrated circuit and the computer, consumer acceptance combined with technological advances has produced an exceptionally strong market for electrical/electronic products that use integrated circuits and computers for the distribution and manipulation of information and data. The integrated circuits are often encapsulated in ceramic packages, mounted on PWB's to form PWA's, and, ultimately, packaged in various electrical or electronic equipment and appliances (i.e., plastic compartments). PWA's have become ubiquitous in such items as personal and business computers, telecommunications equipment, television sets, and other consumer electronic systems. Normal wear-and-tear and the extraordinary rate of technological change in the capabilities PWA's and PWB's have combined to produce a dramatic increase in the amount of obsolete electronic equipment produced in recent years. Despite the fact that much of this unusable or unwanted equipment contains a multitude of hazardous ingredients including copper and lead, much of this equipment is disposed of by simply plating it in private or municipal landfill sites. This approach is problematic for a variety of reasons. For instance, this approach has the potential for leaking toxic materials into the environment (i.e., water table). In addition, this approach unnecessarily dedicates limited landfill capacity. Consequently, consumer, business, and governmental entities are increasingly directed at the ecologically sound disposal of such equipment and have an intensifying interest in recycling the raw materials such equipment contains.
The disposal of PWA's and PWB's, however, involves special problems. Some of the special problems of properly disposing and/or recycling electrical/electronic equipment and appliances relate to the manner in which PWA's and PWB's are manufactured. PWB's are made by laminating two or more layers of fiberglass reinforced epoxy or polyimide resins with copper foil. The laminate is then coated with a metallic material, usually copper, upon which circuits are traced by a variety of imaging and etching techniques. In addition to quality defects that produce unusable PWB's, the process for producing finished, etched PWB's creates up to 20% waste as trim scrap. Because the material from which PWB's are made is a thermoset, the base can not be remelted and reused once it is produced. Similarly, PWA's are produced from PWB's by soldering or otherwise affixing functional components, such as chips of integrated circuit (hereafter "IC's"), connectors and other components to the base. The composition of these components includes such precious metals as Gold, Silver, Palladium and Platinum which are encapsulated in ceramic or epoxy resins.
Some existing techniques dispose of PWA's and PWB's in the following fashion. PWA's may be stripped of any reusable components. The partially depopulated PWA's are then sent to a smelter where they are pyrolized to burn off volatile constituents and then crushed. The resulting ash is then reduced by melting and the precious and semi-precious metals are recovered through several pyrometallurgical stages. The value of the precious metals is then calculated, after subtracting the cost of the smelting process, and this value is returned to the supplier of the PWA's.
This process has several disadvantages when complete PWA's are sent directly to smelters:
the smelting process is inherently costly in term of energy usage; PA1 the pryolsis process produces air pollutants that must be scrubbed from oven stacks or otherwise converted into carbon dioxide, which is an environmentally unfriendly substance; PA1 the resulting "sludge" from the smelting process is returned to the landfill, which uses up limited landfill capacity and, in some circumstances, may leak into the environment; and PA1 sampling techniques to determine the precious metal content of the PWA's prior to the smelting operation are impractical and unreliable.
Alternatives to the direct smelting of PWA's include techniques that seek to separate various metal constituent components from the non-metallic constituent components of complete electrical/electronic systems. These techniques include mechanical crushing of electrical/electronic units followed by magnetic separation to remove ferrous metals, followed either by sink flotation techniques to remove lighter weight non-metallic or metallic constituent components; or by density separation techniques followed by treatment of the resulting metallic or non-metallic portions with strong acids, bases or toxic cyanide; or by elaborate series of grinding and density separation steps to completely separate such metals as copper from aluminum and nickel. These approaches still require hazardous components such as Cathode Ray Tubes (CRT's), mercury switches, and Polychlorobiphenly containing capacitors, frequent components of electronic assemblies, to be removed manually. In addition, they involve chemical or water treatment that requires careful and costly monitoring of effluents for hazardous ingredients and/or are costly with respect to the value of the reclaimed materials.